Hi Rick,
It is a delayed response, but maybe it is still relevant.
I've seen a similar trend with several Pentax lenses that had "SDM" (aka
Micro Ultrasonic, or "old style" micro SDM aka piezoelectric motor).
It's been an issue since the very beginning of 16-50 lens, which, AFAIR,
was the very first lens with then a new type of AF mechanism, and was very
prone to that problem.
It's been a while since I was looking into it, so, I do not remember all
the details of why it was happening, but the main advice was to
"excercise" the AF of these lenses on a regular basis.
Based on my observation, the issue will likely come back, but if you
"excercise" the AF regularly, it might work well for quite long time.
If/when it doesn't seem to work, try autofocusing with it several time, so
that the motor would be activated both ways. In some cases after some
(5-30) back-and-forth attempts, it might start moving, first, slightly,
then getting back to the normal range. Sometimes, if it doesn't work on
the first excercise attempt, try again a bit later.
HTH,
Igor
Rick Womer Wed, 19 Mar 2025 18:50:11 -0700 wrote:
Today I took a photo walk with the photo class I enrolled in. I had intended
to substitute another lens for the 17-70, but forgot to. I focused manually
for several shots, and then the lens woke up and autofocused without problems
for the rest of the morning.
Not sure I trust it, of course…
Rick
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